This invention relates in general to bar coding. More specifically, it provides a bar code label made of a recording medium having a bar code printed thereon and a method for printing a bar code.
A bar code generally includes a plurality of bars having a different optical reflectance than that of a background on which they are printed. The bars are arranged side by side with spaces therebetween to display information. The information may be encoded into the width of the bars, the spacing of the bars or both the width and spacing of the bars.
For example, the bars may be black on a white background (represented by spaces between the black bars). Various bar code schemes are known which are differentiated from one another based on the manner in which information is encoded, such as specific widths, sequences, etc. The various encoding schemes have names such as, for example, "NW-7", "2 of 5", "code 39", etc.
In this connection, a bar code reader is also known which optically reads the width of each bar of a bar code on the basis of a difference in reflectance of the bars with respect to the background. For example, one type of reader reads a bar code by focusing an image of the bar code on an image sensor and converting the image into an electric signal.
In the prior art, it is known to uniformly print the bars of a bar code with a predetermined ratio of bar width to some reference value of width based on the encoding scheme being used. This predetermined ratio is used without regard to the shape of the surface on which the bar code is being applied. Sometimes, a bar code is printed on a curved surface such that the widthwise direction of the bars of the bar code coincide with the circumferential direction of the curved surface. Other times, the bar code may be printed on a seal which is later applied to a curved surface in the same manner. However, the surface curvature can cause a reading error. When a bar code provided on such a curved surface is read by the bar code reader, the width of a bar provided in a portion of the curved surface having a large gradient is detected as if it were narrower than the width of another bar provided in another portion of smaller gradient. Therefore, erroneous readings occur which cause reading efficiency to be low and the dependability of information to also be low.
Further, in the case of providing a bar code on a cylindrical surface, it is general in the prior art to make the widthwise direction of bars parallel to the axial direction of the cylinder. Although this helps to overcome the problem discussed above to some degree, using the axial orientation is very limiting. For price labels, merchandise or boxes must be designed in such a manner to accommodate the axial orientation of the bar code label.
As an example of the problems caused by curved surfaces, consider a bar code label applied to a "belt" around a portion of the human body as shown in FIG. 11. If it is desired to make the axial direction of the belt coincide with the widthwise direction of bars, the belt must be a comparatively large size in its transverse direction.
FIG. 11 illustrates a belt 4 tied around a person's wrist. The belt 4 comprises a holder portion 41 and belt portions 43 and 44 extending in both directions from the holder portion, with the holder portion 41 including a transparent window portion 42. A bar code label 1 is inserted in the holder portion 41, and the belt portions 43 and 44 are coupled together by appropriate clamp means. The belt portions 43 and 44 are provided with a plurality of hooks, magic tapes, etc. so as to be adaptable to a variety of thickness.
Such label holders as above are used in medical institutions to discriminate individual patients, hence, a light feeling of attachment is requested. However, if it is necessary to make the widthwise direction of the bars of a bar code 2 coincide with the axial direction of the belt tied as above, the width E of the holder portion 41 must be larger than desireable. This tends to hinder the patient's movement.